Answer:
Option B
Explanation:
According to the Einstein equation,
$KE_{max}=hv_{0}-\phi _{0}$
where, $KE_{max}$ = maximu kinetic energy and $\phi_{0}$
= work function
Initially , hv= 0.4+ $\phi _{0}$ ........(i)
When the frequency of incident radiation is increased by 30% , then
1.3 hv=0.9 +$\phi _{0}$ .........(ii)
Solving Eqs.(i) and (ii) , we get
$0.3\phi _{0}=0.9-1.3(0.4)$
$\therefore$ $\phi _{0}=\frac{0.38}{0.3}=1.267 eV$
